As is known, after molten steel has been tapped from a furnace into a ladle, it is customary to make additions to the melt in the ladle in order to add alloying agents and produce a product of the desired analysis. Normally, alloying additions are added as ferroalloys such as ferromanganese or ferrochromium, etc. These additions are made by simply introducing the addition agent into the bath as lumps or in suitable containers, such as steel sheet cans or combustible containers. Since the added material is relatively cool, it can reduce the temperature of the melt to the point where problems are encountered when the ladle is poured into ingot molds or the like.
To avoid the problem of cooling by alloying additions, the molten bath must be heated in the furnace to a much higher temperature than otherwise would be necessary, or an exothermic material must be placed in the ladle with the additions in order to create heat that will offset the cooling additions. In the past, such an exothermic reaction has been provided by introducing the ferroalloy, such as ferromanganese, mixed with sodium nitrate and silicon. This results in an exothermic reaction between the sodium nitrate and silicon but results in dense clouds of smoke and a noxious sodium oxide vapor which, of course, pollutes the surrounding atmosphere. Furthermore, the use of sodium nitrate may result in undesirable additions of nitrogen and other inclusions in the melt.
It has been well known for some time that ladle additions of silicon carbide can have beneficial effects in molten steel. Silicon carbide can be used to add silicon and/or carbon; however, more importantly, it produces an exothermic chemical reaction which results in the generation of heat. For that matter, silicon carbide has been mixed with ferroalloys in the past to generate heat and overcome the cooling effect of the alloying additions as is described, for example, in Miltenberger U.S. Pat. No. 3,841,861.